1. Field of the Invention
The present invention relates generally to a heat sink, and more particularly, to an interleaved heat sink structure for dissipating heat from memory chips.
2. Description of the Related Art
Electronic storage medium, such as dynamic random access memory (DRAM), is frequently packaged in a way that allows for high density per unit of physical space. DRAM often dissipates heat as a part of normal operation and functions optimally within a temperature range. This is especially true given the recent proliferation of stacked, doubled sided DRAM dual inline memory modules (DIMMs) where the DRAM packages are stacked in a planar fashion, and where stacked DRAM packages are placed on both sides of a printed circuit board (PCB).
FIG. 1(a) shows a side view of a conventional DRAM DIMM 100 that includes a plurality of DRAM packages 110 attached to both sides of a PCB 120. The DRAM DIMM 100 is plugged into a host board 130 through a DIMM socket 140 and is received by a pair of connectors 150. Multiple DRAM DIMMs are often placed on a host board in rows, columns, or both to maximize memory density in a given physical space. FIG. 1(b) illustrates a top view of a DRAM DIMM array 100′ placed in rows on the host board 130. Each of the DRAM DIMMs is received by a pair of connectors 150.
As shown in FIG. 1(a) and FIG. 1(b), DRAM DIMMs can be actively cooled by transverse airflow. However, in a system where a DRAM DIMM array is placed on a host board in close proximity to each other, such as 12.7 mm, this creates a situation where the air must flow through narrow air channels between the DRAM DIMMs. Given that DRAM DIMMs are generally longer than the placement density of a DRAM DIMM array on a host board, the air channel between two DRAM DIMMs can be very narrow and long. As a result, a boundary layer is developed around each DRAM DIMM, which results in a stagnation of airflow near the DRAM DIMM surface.
As illustrated in FIG. 2, when boundary layers 210 are formed around two DRAM DIMMs, the airflow in the areas 220 between the boundary layers 210 and the DRAM DIMM surfaces are slowed down, thus reducing the efficiency in which heat can be dissipated from the DRAM packages 110 of the PCBs 120. In this example, the airflow is actually more efficient between the areas 220, where it is less effective to cool the DRAM DIMM surfaces.
In order to solve the thermal challenges generated by a DRAM DIMM array, integrated metal heat spreaders, attached to the DRAM DIMM surfaces, can be used to assist with cooling. However, due to the boundary layer effect, the heat that gathers at the metal heat spreaders need to be directed to an area where more air is flowing, such as region 220′. Therefore, it would be useful to design a heat sink that can pass through the boundary layer. This, however, conflicts with achievable DRAM DIMM density because such a heat sink design would reduce the possible density in which DRAM DIMMs could be placed in an array since the heat sink would occupy space that could otherwise be occupied with a denser placement of DRAM DIMMs. If the heat sinks are placed in close proximity to each other, individual servicing, i.e., the individual vertical injection and ejection, of each DRAM DIMM in a DRAM DIMM array might be jeopardized.
In view of the foregoing, there is a need for a heat sink that will highly utilize the airflow between the DIMMs yet still allow high density and individual servicing of each DIMM in a DIMM array.